Crushing and grinding device, a soybean milk maker including said device and a method for making soybean milk

ABSTRACT

The present application discloses a recirculating crushing and grinding device for crushing and grinding liquid-like materials or materials that contain liquid, said device comprises a motor, a hopper, a crushing and grinding part and a material recirculating part. Said crushing and grinding part includes a coarse-crushing section and a fine-grinding section, said fine grinding section comprises a pair of grinding components, and said material recirculating part comprises a pump and recirculating ducts provided downstream of said crushing-grinding part. The present application also discloses a soybean milk maker employing said recirculating crushing-grinding device, and a method for crushing and grinding a recirculated material and a method for producing soybean milk. The equipment disclosed in the present invention is easy to manufacture, with the advantages of a low noise during operation and low energy consumption.

The present application is a divisional of U.S. patent application Ser.No. 11/303,879, filed Dec. 16, 2005 now U.S. Pat. No. 7,478,772, whichis a continuation of International Application PCT/CN2004/000642, filedJun. 15, 2004, all of which are hereby incorporated by reference as iffully set forth herein.

TECHNICAL FIELD

The present invention relates to the field of crushing and grinding, andmore particularly to a crushing and grinding device and a method forcrushing and grinding a recirculated pulp material; and further to asoybean milk maker employing said crushing and grinding device and amethod for making soybean milk.

BACKGROUND

In the conventional colloid mills used in the fields of medical,cosmetic, dope, fine chemical industry and food processing etc., whichare either conical-structured or disc-structured, the milling movementsare small due to the limitation of the size of the mill tool. In orderto achieve a super-fine grinding of a material, the equipment is usuallyof bulky structure. Not only are the manufacturing processes of therotating and stationary mill bodies thereof complicated and costly, butalso the motor has to run at very high speed, generally around 8000rounds per minute, resulting in a loud noise during operation and alarge consumption of power.

In the prior art domestic soybean milk maker, in order to achieveminiaturization, the grinding device is driven by a high-speed motor sothat the crushing blades hit and crush the beans in filter gauze, withsoybean milk filtered through the gauze and then boiled for drinking.Notable disadvantages thereof are: requirement of high rotation speed ofthe blades, large noise caused during operation, a low production rateof soybean milk, small regulating range of soybean milk concentrationand quantity, and difficulty in gauze cleaning. As disclosed inCN2273965Y, “an automatic cycle mini soybean-milk maker of assembledtype”, the grinding device thereof comprises a stator (i.e. a stationarygrinder) and a rotor (i.e. a rotary grinder). The inventor believes thatboth the design and manufacture of the stator and the rotor arecomplicated and difficult, and it is impossible to obtain an integratedstructure under conventional processes and technology, thus an assembledarrangement is employed for the stator and rotor, which results in alarge number of mill parts, huge labor in assembling, and a high failurerate. Its operation principle is that material is pulled and pushed andthus crushed and ground by a cyclic force caused by the high-speedrelative motion between the assembled stator and rotor, so that thematerial “escapes with high speed from the lower annular gap after beingground”. Thus, the high rotation speed also brings about a disadvantageof large noises.

CONTENTS OF THE INVENTION

In view of above-mentioned disadvantages in the conventional colloidmills, the aim of present invention is to provide a crushing andgrinding device for grinding liquid-like materials or materials thatcontain liquid, and a method thereof. Said device can be miniaturizedand manufactured easily, with a low noise and low energy consumption.

The present invention also provides a soybean milk maker and a methodfor making soybean milk. Said soybean milk maker employs said crushingand grinding device and is capable of overcoming the problems existingin the prior art soybean milk maker, such as large noises, low milkproduction rate, etc. Said soybean milk maker is suitable for bothhousehold and commercial use.

The crushing and grinding device provided in the present inventionmainly comprises a motor, a hopper, a crushing and grinding part and amaterial recirculating part, characterized in that said crushing andgrinding part includes a coarse-crushing section and a fine-grindingsection, said fine grinding section comprises a pair of grindingcomponents, and said material recirculating part includes a pump andrecirculating ducts provided downstream of said crushing and grindingpart.

Since the crushing and grinding device provided in the present inventioncomprises a coarse-crushing section and a fine-grinding section, andmaterials are recirculated through the coarse and fine grinding sectionsthrough an exterior recirculating mechanism, the rotation speed of thegrinding components can be greatly reduced; thus the noise and energyconsumption are reduced, too.

The present invention also provides a method for crushing and grindingliquid-like materials or materials that contain liquid. Said methodincludes the processes of material feeding, material crushing andgrinding and material recirculating, characterized in that the materialis finely ground after being coarsely crushed, then is recirculatingoutside of a crushing and grinding chamber through a pump andrecirculating ducts which are provided downstream of the crushing andgrinding part, so as to improve the fineness and uniformity of materialparticles in the slurry. The rotor has a rotation speed of 1000˜3000rounds per minute during crushing and grinding process.

In order to reduce noise and failure rate of a soybean milk maker and toimprove the production rate of milk, the present inventor applies abovecrushing and grinding device in a soybean milk maker. A soybean milkmaker employing such crushing and grinding device comprises amilk-producing section, a milk-boiling section and a circuit controlsystem. The milk-producing section thereof includes a motor, a hopper, awater tank, a crushing and grinding part and a material recirculatingpart, the milk-boiling section thereof comprises an electric heatingdevice and a boiling cup, the circuit control system thereof comprises acontrol circuit board and a control valve assembly, characterized inthat said crushing and grinding part includes a coarse-crushing sectionand a fine-grinding section, said fine grinding section comprises a pairof grinding components; and said material recirculating part comprises arecirculating pump, a control valve assembly and corresponding ductswhich are provided in the downstream of said crushing and grinding part.An outlet of the recirculating pump is connected with an inlet of saidcontrol valve assembly, and one end of said recirculating duct isconnected with an outlet of said control valve assembly, and the otherend of said recirculating duct leads to the hopper.

A soybean milk maker of this type provided in the present invention isadvantageous in that it is compact in structure, easy to assemble, withlow failure rate and low noise. Furthermore, the milk production rate ishigh and it is easy to clean.

The present invention also provides a method for making soybean milk.The said method includes processes of material feeding, crushing, slurryproducing and milk boiling, characterized in that the soybean iscoarsely crushed and then is finely ground, after that, the groundmaterial is recirculated outside of a crushing and grinding chamberthrough recirculating ducts, so as to improve the fineness anduniformity of material particles in the slurry. The rotor operates at arotation speed of 1000˜3000 rounds per minute during the crushing andgrinding process.

In the above method, in order to further improve the milk productionrate and the taste of the resulting soybean milk, water that is fed tothe material is heated to 80° C.˜95° C. before the material has beencrushed and ground. The present invention also provides a water tank.Water in said tank can be pre-heated by a heating element so that thetemperature of the slurry can be surely kept between 70° C.˜93° C. whenthe slurry is recirculated outside the crushing and grinding chamber.The heated water in the water tank can also be used to clean the milkproducing device automatically after milk producing procedures have beenfinished, so that the problem that the milk producing device isdifficult to clean is also resolved.

When the crushing and grinding device of the present invention is usedto grind materials, and when the soybean milk maker of the presentinvention is used to produce soybean milk, the rotor, preferably,operates at a rotation speed of 2800˜2900 rounds per minute during thecrushing and grinding process, which will not only satisfy the technicalrequirements, but also have the operation noise controlled within therange of 50˜60 decibel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural schematic drawing of an embodiment of a crushingand grinding device according to the present invention;

FIG. 2 is a cross-sectional view along line A-A of FIG. 1;

FIG. 3 is a cross-sectional view along line C-C of FIG. 1;

FIG. 4 is a partially enlarged view of a grinding chamber;

FIG. 5 a-5 b are top plan views of a crushing blade;

FIGS. 6 a-6 c are vertical cross-sectional views of three kinds ofcrushing blade;

FIG. 7 is a cross-sectional view of an embodiment of the soybean milkmaker according to the present invention;

FIG. 8 is a staggered sectional view along line E-E of FIG. 7;

FIG. 9 is a top plan view of FIG. 7.

In these drawings, following elements are indicated: 1. hopper; 2.crushing blade; 3. retainer ring; 4. crushing chamber; 5. top seal ringof the stationary grinder; 6. stationary grinder; 7. rotary grinder; 8.impeller; 9. bottom seal ring of the stationary grinder; 10. motorshaft; 11. motor front cover; 12. seal ring of the motor shaft; 13.bearing of the motor shaft; 14. motor rotor; 15. motor casing; 16. motorback cover; 17. outlet duct; 18. recirculating duct; 19. control valveassembly; 20. slurry discharge duct; 21. cap for the seal ring of themotor shaft; 22. circuit controller; 23. fan blade; 24. expellingoutlet; 25. hopper cover; 26. water feeder; 27. inlet duct of the waterfeeder; 28. recirculating duct for feeding slurry; 29. blowhole of thewater feeder; 30. housing; 31. slurry inlet; 32. filter; 33. controlcircuit board; 34. anti-overflow electrode support; 35. anti-overflowelectrode; 36. cap of the boiling cup; 37. boiling cup; 38. handle ofthe boiling cup; 39. drain duct; 40. electric heating discus; 41. base;42. fixing plate of the heating device; 43. temperature sensor; 44.electrical heating tube; 45. water tank; 46. outlet duct of the waterpump; 47. inlet duct of the water pump; 48. water level sensor; 49.water pump; 50. water intake valve; 51. control panel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The present invention will be further discussed in conjunction with theaccompanying drawings and embodiments to give a better description ofthe present invention.

FIGS. 1, 2, 3, 4 show a preferred embodiment of a crushing and grindingdevice of the present invention. A fine grinding section of said deviceincludes a stationary grinder 6 and a rotary grinder 7 with mill teethdistributed uniformly on the inner wall of the stationary grinder 6 andthe outer wall of the rotary grinder 7. The rotary grinder 7 is fittedinside the stationary grinder 6 with a dynamic rotating gaptherebetween, the gap size being around 0.03˜0.6 mm. The lower end ofthe stationary grinder 6 is fixed on a motor front cover 11 throughbolts, with a bottom seal ring 9 of the stationary grinder providedbetween the lower side of the stationary grinder 6 and the motor frontcover 11; the rotary grinder 7 is securely fitted on a motor shaft 10with axial alignment and is fastened to the front end of the motor shaft10 by screws; crushing blade 2 is integrally formed on the upper endsurface of the rotary grinder 7 so that a coarse crushing section isformed. A recirculating system comprises a hopper 1, an impeller 8 of animpeller pump in a crushing and grinding chamber, an outlet duct 17, acontrol valve assembly 19, a recirculating duct 18 and a slurrydischarge duct 20; the hopper 1 with a repose angle β is fixedly screwedon the outer wall of the upper end of the stationary grinder 6, and atop seal ring 5 of the stationary grinder is provided at the top end ofthe stationary grinder 6 to ensure sealing; an outlet 24 is provided onthe motor front cover 11; the impeller 8 of the impeller pump isarranged below the rotary grinder 7, and the impeller 8 is co-axial withthe rotary grinder 7. In said embodiment, the impeller 8 and the rotarygrinder 7 are integrally configured so that the structure of the entirerecirculating crushing device is compact. The outlet duct 17 isconnected with an inlet of the control valve assembly 19, and one end ofthe recirculating duct 18 is connected with one outlet of the controlvalve assembly 19, while the other end of the recirculating duct 18leads to the hopper 1, and one end of the slurry discharge duct 20 isconnected with the other outlet of the control valve assembly 19; acircuit controller 22 is connected with the motor and the control valveassembly 19; the motor front cover 11 is fastened on the motor casing 15by bolts, and a shaft bearing 13 for the front end of the motor shaft 10is securely embedded in the motor front cover 11, and a seal ring 12 ofthe motor shaft is provided above the motor shaft bearing 13, on thefront end surface of which a capping 21 for the motor shaft seal ring ispressed. The motor can be forcedly cooled through the fan blades 23.

The control valve assembly 19 may be an electromagnetic valve, anelectrically controlled change valve, and so on.

The repose angle β of the hopper 1 is between 25°˜40°, most preferablybetween 29°˜35°, so that materials in the hopper 1 can flow downwardsmoothly.

As shown in FIG. 4, a retainer ring 3 is provided at the lower end ofthe hopper 1 to prevent the material from overflowing upwardly duringcrushing, so as to ensure that the material is circulated through thecrushing and grinding chamber from the top down to the bottom. When therotary grinder 7 has a diameter of 46 mm, the inner diameter D of theretainer ring 3 should be between 15˜50 mm, most preferably between36˜38.5 mm. When said size is between 36˜38.5 mm, the device can grindat high speed and with high efficiency, while a smaller or larger sizewould lead to an non-smooth down-flow of the material or result in asmall amount of the material being unable to enter into the crushingchamber 4 when the grinding process approaches the end. Meanwhile, theheight H of the crushing chamber 4 should be between 10˜35 mm, mostpreferably between 18˜21 mm. In this most favorable height range, thedevice can achieve a high grinding velocity and a high efficiency. It isdifficult for the material in the hopper 1 to enter into the crushingchamber 4 when H is greater than said value, or the material may notflow down smoothly when H is less than said value. Another factor thataffects the grinding speed is the height h of crushing blades 2. Whenthe rotary grinder 7 has a diameter of 46 mm, the height h of thecrushing blade 2 should be between 3˜20 mm, most preferably between 7˜10mm. A slow grinding may occur if h is less than said value, while thedevice tends to get blocked if h is greater than said value so that itfails to run correctly.

Meanwhile, the shape of the crushing blade 2 can also affect thegrinding speed. A preferred structure of the crushing blade 2 is shownin FIG. 5 a or 5 b. A crushing blade 2 includes a main blade area A₁, atransition area A₂, and a secondary blade area A₃. The outer edges ofthese areas can be broken lines as shown in FIG. 5 a or a curved line asshown in FIG. 5 b, with smooth transition at the connections of saidbroken lines. The main blade area A₁ serves to pre-crush and take in thematerial particles, the transition area A₂ serves to transit thepre-crushed material to the secondary blade area A₃, and the secondaryblade area A₃ serves to eventually feed the delivered material to thecrushing chamber between the rotating and stationary grinder. Said mainblade area A₁ of the crushing blades has an inclination α, i.e. ∠T₁O₁N,of 100°˜165°, most preferably 135°˜145°, while the rake angle θ ofsecondary blade area A₃, i.e. ∠PO₂T₂, is 10°˜70°, most preferably35°˜50°; a distance from the crushing blade vertex O₁ of the feed inletof the main blade area A₁ to the outer edge N of the rotary grinder 7,i.e. X, is 2˜15 mm, most preferably 3˜8 mm, and X is most preferablybetween 6.5˜7.5 mm when the diameter φ of the rotary grinder 7 is 46 mm.This distance can lead to an optimum feed angle and improvement of thegrinding speed of the device. The vertical contour line Y of thecrushing blade 2 can be an arc line shown in FIG. 6 a or a straight lineshown in FIG. 6 b or 6 c which may be employed for different grindingmaterials, no matter the crushing blade 2 has a configuration of FIG. 5a or FIG. 5 b.

In the present embodiment, the rotary grinder 7 and stationary grinder 6are both of formed with spurs, with a 0.03˜0.6 mm dynamic gap betweenthe rotary grinder 7 and the stationary grinder 6; the rotary grinder 7and stationary grinder 6 can also have a skewed-tooth or tapered-toothconfiguration; they can be single stepped or multiple stepped; thecross-section of the teeth may be rectangular, stepped-shaped, or oftaper.

The fine grinding section consisting of the stationary grinder 6 androtary grinder 7 can also be replaced by a pair of millstonescounter-rotating with each other, and the grinding surface thereof maybe horizontal.

The coarse crushing section and fine grinding section of the crushingand grinding device may be integrally formed as shown in FIG. 1, andthey may separate from each other, for example, the crushing blade 2 maybe separately mounted on the motor shaft 10. In another preferredembodiment of an integral structure, the gap between the top ends of thestationary grinder 6 and the rotary grinder 7 can be enlarged to form aV-shaped opening, so as to directly form the coarse crushing sectionwhich, in place of the crushing blade 2, primarily crushes the materialparticles and makes them enter into the fine grinding section downstreamfor further grinding. The gap size of the opening depends on the size ofmaterial particles to be crushed.

The impeller 8 of the pump employed in the recirculating system can alsobe an independent impeller and is mounted on the motor shaft 10. Saidpump can be any suitable liquid pump in the prior art, which can also bemounted outside the grinding chamber.

The steps for the crushing and grinding process are as following:

-   -   (a) putting the liquid-like materials or materials that contain        liquid which are to be crushed into the hopper 1;    -   (b) initiating the motor according to programmed procedures        through the circuit controller 22 so as to drive the rotary        grinder 7, the crushing blades 2 at the top of the rotary        grinder and the impeller 8 of the impeller pump, and the control        valve assembly 19 is set to circulation state;    -   (c) under the suction of the impeller 8 of the impeller pump,        the material crushed by the crushing blade 2 and ground between        the rotary grinder 7 and stationary grinder 6 is fed back into        the hopper 1 by passing through the expelling outlet 24, the        outlet duct 17, the control valve assembly 19 and the        recirculating duct 18;    -   (d) when the material meets the milking production standard        after continuous recirculation through the crushing and grinding        part, the circuit controller 22 operates the control valve        assembly 19 according to the programmed procedures so that the        control valve assembly 19 is in a state to discharge the slurry,        the slurry then is discharged from the slurry discharge duct 20;    -   (e) the circuit controller 22 controls the motor according to        the programmed procedures so that the motor is in a stand-by        state, and the whole grinding process is finished.

After the slurry has been completely discharged, a cleaning process canbe started. The device can be cleaned automatically by adding cleaningliquid from the hopper then repeating the above-described process.

Of course, for some materials, to meet the crushing requirements, uponusing of the present crushing and grinding device, repeated crushing andgrinding is not necessary. In this case, the present crushing andgrinding device can directly discharge the crushed and ground materialsunder the control of the control valve 19.

According to the prior art, the rotary grinder 7 can also be connectedto the motor shaft through a coupling joint. Obviously, the structure ofthis coupling arrangement is relatively complex, and it brings about ahigher installation requirement.

Embodiment 2

As shown in FIGS. 7, 8, 9, a preferred embodiment of soybean milk makeraccording to present invention comprises a milk-producing section, amilk-boiling section and a circuit control system:

-   -   (a) The milk-producing section comprises a milk-producing        device, a water supplying system, a recirculating system, a        motor and a control circuit board. The milk-producing device        mainly takes the form of the crushing and grinding device        according to Embodiment 1 to crush and grind beans and peas        materials, wherein the structures, shapes and connections of the        hopper 1, crushing blades 2, retainer ring 3, crushing chamber        4, top seal ring 5 of the stationary grinder, stationary grinder        6, rotary grinder 7, impeller 8, bottom seal ring 9 of the        stationary grinder, motor shaft 10, motor front cover 11, seal        ring 12 of the motor shaft, bearing 13 of the motor shaft, motor        rotor 14, motor casing 15, motor back cover 16, outlet duct 17,        capping 21 for the seal ring of the motor shaft and fan blade 23        are all same as those in the crushing and grinding device of        Embodiment 1, or may employ other alternative arrangements        described in Embodiment 1. The water supplying system includes a        water tank 45, a water pump 49, an inlet duct 47 of the water        pump, an outlet duct 46 of the water pump, a water intake valve        50, a water feeder 26 and an inlet duct 27 of the water feeder.        A heating device is provided in the water tank. A fixing plate        42 for the heating device and a water level sensor 48 are        secured on the wall of the water tank 45, and an electrical        heating tube 44 and a temperature sensor 43 are inserted on the        fixing plate 42 for the heating device. The water intake valve        50 is connected with the water tank 45. The recirculating system        comprises the impeller 8 of the impeller pump, a recirculating        duct 28 for feeding slurry, the outlet duct 17, the        recirculating duct 18, the slurry discharge duct 20 and a drain        duct 39. An electrically controlled change valve may be taken as        the control valve assembly 19. A boiling cup 37 communicates        with the other outlet of the electrically controlled change        valve via the discharge duct 20. The expelling outlet 24 is        connected with the outlet duct 17, while the other end of the        outlet duct 17 is connected to the inlet of the electrically        controlled change valve. One end of the recirculating duct 18 is        connected with an outlet of the electrically controlled change        valve, and the other end thereof connected with the        recirculating duct for feeding slurry 28 secured on the water        feeder 26. One end of the slurry discharge duct 20 is connected        with the other outlet of the electrically controlled change        valve, and the other end thereof is coupled to the slurry inlet        31 on the cap 36 of the boiling cup with the centers thereof        aligned. One end of the drain duct 39 is connected to a drain        device (not shown in Figures, may be a container, or a        connecting duct leading to a cloacae), and the other end thereof        is connected to an outlet of the electrically controlled change        valve. The control circuit board 33 is connected with the motor        and the electrically controlled change valve. The water feeder        26 is clapped on a hopper cover 25. An outlet duct 46 of the        water pump is connected with the inlet duct 27 of the water        feeder 26. The water feeder 26 distributes water so that water        flows down along walls of the hopper 1.    -   (b) The boiling cup 37 of the milk-boiling section is provided        on an electrical heating discus 40. The bottom of the boiling        cup 37 is preferred to be spherical, and said sphere R is        preferred to be consistent with the top sphere R of the        electrical heating discus 40 so as to achieve a larger thermal        conducting area. The electrical heating discus 40 is fastened on        a base 41 by screws. The slurry inlet 31 fixed on the cap 36 of        the boiling cup is coupled to the slurry discharge duct 20 with        centers thereof aligned. While an anti-overflow electrode 35        fixed on the cap 36 of the boiling cup is connected with an        anti-overflow electrode support 34 secured on the housing 30 in        the manner of elastic contact. In addition, the electrical        heating discus 40 can also be embodied as an electromagnetic        heating component. The boiling cup 37 may be taken off by means        of a handle 38 of the boiling cup.    -   (c) The circuit control system comprises a control circuit board        33 and a control panel 51. The control circuit board 33 is        connected with the motor, the electrically controlled change        valve, the water pump 49, the water intake valve 50, the        electrical heating tube 44 and temperature sensor 43 in the        water tank 45, the water level sensor 48 on the water tank 45,        the electrical heating discus 40, the anti-overflow electrode        support 34, and the control panel 51 provided on the housing 30,        respectively (neither connecting wires nor specific structure of        the control circuit board are shown in Figures, and it is not        difficult for an ordinary person skilled in the art to realize        these features), to control the processes, such as feeding water        into the water tank, heating water in the water tank, feeding        the hopper with water, and so on. To facilitate a user to        disassemble and use the soybean milk maker according to present        invention, and to guarantee safety and sanitary condition, the        hopper cover 25 of the milk producing device in the soybean milk        maker according to the present invention is preferably connected        with the housing 30 through a hinge structure, and all ducts are        made of special food-safe materials. In addition, all of the        ducts interconnects with each other through inserting & snapping        structures.

When the water feeder 26 supplies water to the hopper 1, in order tofacilitate the materials to flow downward more smoothly, especially tofacilitate cleaning the milk producing, it is preferred to connect theinlet duct 27 of the water feeder to the water feeder 26, and to provideblowholes 29 on the water feeder 26, through which water is supplied tothe hopper 1, more specifically, the water is sprayed to the inner wallsof the hopper by the blowholes. Thus not only materials adhered on theinner wall of the hopper 1 can be rinsed off, which is advantageous forthe down-flow of the material, but also foams produced in the hopper 1is reduced during the recirculating milk producing process.

Turn on the soybean milk maker, then the control circuit board 33 getsinto its operating state and gives an instruction to the water intakevalve 50 to automatically feed water into the water tank 45. When thewater level reaches the design value, the water level sensor 48 on thewall of the water tank 45 sends a signal to the control circuit board33, and the control circuit board 33 gives an instruction to the waterintake valve 50 to stop water feeding (the operating principle of such adevice is similar to that of a water-feeding device in a fully-automaticwasher of prior art, and will not be described here), then the soybeanmilk maker gets ready for the next operation procedure which wasdescribed above. Thus, the degree of automation is improved and theequipment is more convenient to use.

In a preferred embodiment of a soybean milk maker according to thepresent invention, as shown in FIG. 7, a filter 32 is screwed on theslurry inlet 31 of the cap 36 of the boiling cup. Said filter 32 caneither be a rigid filter mesh or a flexible filter bag, which is usedfor filtering the soybean slurry to fit the taste of a user who favors afiner soybean milk. The filter 32 may be taken off from the slurry inlet31 while cleaning, and may be screwed on the slurry inlet 31 aftercleaning. The operation is easy and convenient.

The control valve assembly 19 may also be configured as anelectromagnetic valve assembly. But an electrically controlled changevalve, compared with an electromagnetic valve assembly, which isemployed in a soybean milk maker would lead to a space saving andreduction in parts numbers. Since the valve body of a change valvecannot keep water or sediments, and opening, closing, changeover,sealing thereof are more reliable, the lifespan of the soybean milkmaker is extended.

The milk producing procedures of a soybean milk maker according to thepresent invention are:

-   -   (1) feeding soaked soybeans or dry soybeans into the hopper,        then turning on the power via the control panel;    -   (2) feeding water into the water tank, and pre-heating the water        to a predetermined temperature under the control of the control        circuit board;    -   (3) a water pump supplies heated water to the hopper, and a        motor of a recirculating crushing and grinding device operates        to produce slurry;    -   (4) under the control of the control circuit board, the final        soybean milk produced according to the design procedures is        discharged into the boiling cup and boiled therein then poured        out for drinking;    -   (5) the water pump is controlled by the control circuit board to        feed the hopper with water once again, the motor of the        recirculating crushing and grinding device is operated to clean        the recirculating crushing and grinding device, and dirty water        is discharged through the drain duct; and,    -   (6) the control circuit board 33 controls the equipment so that        the equipment is in a stand-by state, and all processing        procedures are finished.

1. A soybean milk maker, comprising: a milk-producing section includinga crushing and grinding device, said crushing and grinding devicecomprising a motor, a hopper, a crushing and grinding unit, and amaterial recycling part, said material recycling part comprising a pumpand recycling ducts downstream of said crushing and grinding unit, saidcrushing and grinding unit comprising a coarse-crushing section and afine-grinding section, wherein said fine-grinding section comprises astationary grinder and a rotary grinder, said coarse-crushing section islocated in a chamber of the stationary grinder, and said coarse-crushingsection includes a crushing blade, wherein a gap between the outer sidesurface of the crushing blade and the inner surface of the stationarygrinder chamber gradually decreases in a direction of rotation of thecrushing blade from a leading portion of the crushing blade to a baseportion of the crushing blade, thereby forming a crushing chamber; amilk-boiling section comprising an electrical heating device and aboiling cup; and a circuit control system comprising a control circuitboard and a control valve assembly.
 2. A soybean milk maker according toclaim 1, wherein the crushing blade includes a main blade area, atransition area and a secondary blade area, outer edges of these areasbeing defined by broken lines or curved lines, and the connections ofsaid broken lines are smoothly transited, said main blade area has aninclination (α) of approximately 100° to 165°, while the inclination (θ)of the secondary blade area is approximately 10° to 70°, and a distance(X) at a feeding inlet of the main blade area is approximately 2 to 15mm.
 3. A soybean milk maker according to claim 1, further comprising awater tank, wherein a heating device is arranged in said water tank, andwater in said water tank enters into the hopper through a water feeder,said water feeder then distributes water in such a manner so that waterflows down along the hopper walls.
 4. A soybean milk maker according toclaim 2, further comprising a water tank, wherein a heating device isarranged in said water tank, and water in said water tank enters intothe hopper through a water feeder, said water feeder then distributeswater in such a manner so that water flows down along the hopper walls.5. A soybean milk maker according to claim 1, wherein the crushing bladehas a height (h) of approximately 3 to 20 mm, when the diameter of therotary grinder is 46 mm.
 6. A soybean milk maker according to claim 2,wherein the crushing blade has a height (h) of approximately 3 to 20 mm,when the diameter of the rotary grinder is 46 mm.
 7. A soybean milkmaker according to claim 1, wherein said rotary grinder and stationarygrinder both comprise teeth in the form of spurs, and a gap between saidrotary grinder and stationary grinder is in a range of approximately0.03 to 0.6 mm.
 8. A soybean milk maker according to claim 2, whereinsaid rotary grinder and stationary grinder both comprise teeth in theform of spurs, and a gap between said rotary grinder and stationarygrinder is in a range of approximately 0.03 to 0.6 mm.
 9. A soybean milkmaker according to claim 1, wherein said pump is an impeller pump, andthe impeller of said impeller pump is located below the rotary grinderand is fitted on a common shaft with the rotary grinder.
 10. A soybeanmilk maker according to claim 2, wherein said pump is an impeller pump,and the impeller of said impeller pump is located below the rotarygrinder and is fitted on a common shaft with the rotary grinder.
 11. Asoybean milk maker according to claim 1, wherein said impeller of saidimpeller pump is integrally formed with the rotary grinder.
 12. Asoybean milk maker according to claim 2, wherein said impeller of saidimpeller pump is integrally formed with the rotary grinder.
 13. Asoybean milk maker according to claim 1, wherein a retainer ring isprovided at the bottom end of the hopper.
 14. A soybean milk makeraccording to claim 2, wherein a retainer ring is provided at the bottomend of the hopper.
 15. A soybean milk maker according to claim 13,wherein the inner diameter of said retainer ring is 15 to 50 mm, whenthe rotary grinder has a diameter of 46 mm.
 16. A soybean milk makeraccording to claim 14, wherein the inner diameter of said retainer ringis 15 to 50 mm, when the rotary grinder has a diameter of 46 mm.
 17. Asoybean milk maker according to claim 1, wherein the crushing chamberhas a height (H) of approximately 10 to 35 mm.
 18. A soybean milk makeraccording to claim 2, wherein the crushing chamber has a height (H) ofapproximately 10 to 35 mm.
 19. A soybean milk maker according to claim1, wherein said hopper has a repose angle (β) of approximately 25° to40°.
 20. A soybean milk maker according to claim 2, wherein said hopperhas a repose angle (β) of approximately 25° to 40°.